Many thermal sensors have deficiencies. For example, in an approach, a bipolar transistor (BJT) is used as part of a sensor. The BJT has a voltage Vbe drop across a base and an emitter of the BJT. By operation of the BJT, voltage Vbe varies as temperature varies. Further, the temperature coefficient of the sensor is not linear. As a result, temperature variations with respect to Vbe changes cannot be measured with high accuracy.
In another approach, two BJTs are used in two branches of the sensor. In some applications, additional circuitry is used in conjunction with the sensor. Exemplary additional circuitry includes a temperature independent current source and a “chop” circuitry. The chop circuitry is used to cancel noise and current mismatch. The additional circuitry adds complexity to the sensor.
Like reference symbols in the various drawings indicate like elements.